In PRE-CELL the investigators propose to enroll a cohort of early-stage HD patients in a prospective observational study designed to characterize clinical, neuro-imaging, laboratory and biomarker correlates of disease progression over 12-18 months. Subjects who complete a minimum of 12 months' participation in this trial will be candidates for enrollment in the future planned Phase 1 trial of intrastriatal delivery of mesenchymal stem cell (MSC)/Brain-derived neurotrophic factor (BDNF).